Hydrogen fuel is used in a wide variety of commercial applications, such as, e.g., transportation, chemical production, and refineries, to name only a few examples. Due to the explosive nature of hydrogen gas, there is a need to detect hydrogen gas leaks economically, safely and reliably.
Several types of hydrogen sensors are available, including hydrogen field-effect transistor (FET) sensors, thin film and thick film metallic sensors, and fiber-optic sensors. These sensors typically employ a palladium film as a catalyst. Molecular hydrogen coming into contact with the palladium dissociates on the surface, and atomic hydrogen diffuses through the film. Physical or optical changes in or adjacent to the film are used to detect the presence of hydrogen. For example, the light being transmitted in an optical sensor decreases in response to the presence of hydrogen. The change in transmittance corresponds to the amount of hydrogen that is present.
These hydrogen sensors need to respond quickly to the presence of hydrogen, e.g., well before an explosive limit of four percent in air is reached, so that there is sufficient time for corrective action or evacuation. However, some sensors have thin films that are not sufficiently stable upon cyclic exposures to hydrogen. Some sensors have thin films that undesirably foul due to impurities and pollutants when they react with air. Some sensors have thick films or thin films that are unstable with repeated exposure to hydrogen, or excessive concentrations of hydrogen. Some sensors have palladium films that foul due to impurities and pollutants in the air, such as, e.g., hydrocarbons, carbon monoxide, and sulfur bearing substances.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.